background_vspeed[0...7];
Returns: Real
By setting this variable array to a different value, you can set the speed at which GameMaker: Studio automatically scrolls a background for you along the vertical plane. A positive
value will scroll from top to bottom, while a negative value will be bottom to top and 0 stops all scrolling. if you have also enabled vertical tiling, either through the room editor or by using the
background_vtiled variable, then scrolling the background will make it loop infinitely.
if background_vtiled[0] = true
{
background_vspeed[0] = 2;
}
The above code checks background0 to see if it is tiled vertically, and if it is it then sets the vertical scroll speed to 2.